At the sixth hour of the second watch, the rhythmic pounding of star drills shook the foundations of Entry hall 349.
Zhu Heling, having failed with acid, had committed his hired blades to manual sapping. Abandoning the drainage trench, the raiders had moved to the base of the southern outside pier, using air-powered star drills powered by their void-boat’s backup boiler to chip away at the bedrock shelf beneath the arch.
The noise was a brutal, bone-shaking loud noise that echoed through forty leagues of stone: thud-thud... Clank-thud. Every blow of the four-inch heavy dark metal-hardened carbon-iron bits sent blast waves through the dark rock. It shook loose hundreds of years of hardened dust from the high ceiling roof ledges.
Qiao Ming sat upon his three-legged stool in the gatehouse, his horn lantern resting on the floor between his bare feet. He held his Folded brass star-compass against the stonework of the southern pier, measuring the shaking and the shear shifted weight.
The instrument showed that the hired blades had excavated one point four cubic yards of solid mountain stone from beneath the outer toe of the pier. The leftover bearing capacity had declined to ninety-four point two percent. It was still well within the four-fold safety margin established by the First Epoch builders. But the rate of shaking was beginning to cause tiny cracking in the decorative plaster of the inner gallery.
